The major objective of the work in progress is to identify and define some of the inflammatory mechanisms involved in periodontal disease(s). The emphasis is placed on the role of polymorphonuclear leukocytes (PMN) and related factors such as complement. The clinical approach to this problem consists of the study of the changes in various parameters of inflammation during experimental gingivitis and pre- and post-therapy in cases of more advanced periodontal disease. Parameters that are being measured are changes in PMN numbers, cell surface markers and function in the blood and saliva, changes in complement component profiles in serum and gingival fluid; changes in the PMN chemotactic system, both cellular and humoral; and changes in the lymphocyte response to a variety of plaque antigens and mitogens. The disease state in all cases is being monitored by a variety of clinical indices. These studies should enable us to construct functional profiles of PMN responsiveness in gingivitis and other periodontal disease(s) and will provide insight into the role of PMNs in disease. Studies on the effect(s) of PMNs and lymphocyte function and lymphocytes on PMN function are also underway. These experiments are designed to give us an insight into understanding the potential significance of inflammatory cell interactions in such inflammatory lesions as those seen in periodontal disease(s).